Colle San Martino

Overview

Colle San Martino is a long Category 1 climb that stretches 18.3 km from a low start at 87 m to a summit of 1115 m. Across that distance it gains 1028 m of net elevation, and because the road pitches and dips along the way, the total ascent adds up to 1068 m — 40 m more than the net figure alone. The average gradient of 5.62% sounds gentle, and for long stretches it genuinely is, but that number hides a maximum ramp of 18.53% that turns this from a tempo effort into a climb that demands real respect and a plan.

How the Gradient Unfolds

The defining feature of Colle San Martino is the gap between its average and its peak. A 5.62% mean over 18.3 km is a rhythm climb — the kind of gradient you can settle into and hold for the better part of an hour. But an 18.53% maximum is more than three times that average, so the road is far from uniform. Expect shallower drags where you can carry speed, broken up by pitches that spike hard enough to force you out of the saddle. The 40 m difference between the 1068 m total ascent and the 1028 m net gain confirms there are false flats or brief descents built into the profile, meaning momentum lost on the steep ramps can't always be recovered on the way up.

Pacing Notes

On a climb this long, discipline beats bravado. Ride the early kilometres a touch under what feels sustainable, because the 18.53% ramps will extract their toll later and you want reserves when they arrive. Anchor your effort to your FTP: holding the shallower 5.62%-ish sections just below threshold leaves headroom to absorb the steep pitches without blowing up. On the hardest ramps your power will spike well above FTP for short bursts — that's fine, provided you back off immediately once the gradient eases. If you don't know your threshold, run the numbers through the FTP estimator before you commit, and pace the full 18.3 km to that figure rather than to feel.

Gearing

With 18.3 km of climbing and ramps hitting 18.53%, gearing is where this climb is won or lost. A compact 34-tooth inner chainring is the sensible starting point. Pair it with at least a 34×32 for the steep sections — that ratio gives you a survivable cadence when the road rears up. If you climb at a lower cadence, carry extra weight, or simply want insurance for a nearly-19% wall late in an 18.3 km effort, step up to a 34×34. The lower ratio costs you nothing on the 5.62% averages and buys precious margin on the ramps, keeping your legs turning instead of grinding to a halt.

Summary

Colle San Martino rewards patience: a long, honest Category 1 climb whose modest 5.62% average masks brutal 18.53% pitches. Pace it below threshold, gear low, and let the 1028 m of gain come to you.

Length: 18.3 km
Average gradient: 5.62%
Max gradient: 18.53%
Start: 87 m
Summit: 1115 m
Net gain: 1028 m
Total ascent: 1068 m
Category: 1